Post on 30-Jul-2020
Hydrology Presentation: Existing and with-Project
Hydrology
Technical Workgroup Meeting February 14, 2013
Prepared by: Tetra Tech
Prepared for: Alaska Energy Authority
Background
• USGS developed 61 year extended discharge record
• HEC-ResSim model used to simulate operations for a maximum load
following “bookend” scenario to develop hourly with-Project
outflows (“Maximum Load Following Operation Scenario 1”)
• HEC-ResSim Muskingum-Cunge procedure with 1980s cross-sections
used to route the flows downstream to Sunshine
• Both Pre-Project and Maximum Load Following OS-1 conditions
analyzed
• Flow duration and peak flow analysis performed to provide initial
comparison of the Maximum Load Following OS-1 scenario and Pre-
Project conditions
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Basis and Assumptions
• Maximum Load Following OS-1 scenario assigns load fluctuation of the entire Railbelt to Watana
• Prepared for planning purposes – Watana load is very conservative for any period of time and not realistic for an entire year
• Hourly open-water flow routing results from HEC-ResSim • Uses 1980s cross-sections and HEC-2 rating curves • Railbelt generation loads from the 2010 Railbelt Integrated
Resources Plan
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Average Monthly and Annual Flows (cfs)
Period
Watana Dam
(PRM 187)
Susitna River at Gold Creek
(PRM 140)
Susitna River at Sunshine
(PRM 87.9)
Susitna River at Susitna
Station (PRM 29.9)
Pre-Project Max LF OS-1 Pre-Project Max LF OS-1 Pre-Project Max LF OS-1 Pre-Project Max LF OS-1
JAN 1,280 8,840 1,590 9,140 3,720 11,300 7,910 15,500
FEB 1,130 9,450 1,420 9,750 3,260 11,600 7,080 15,400
MAR 1,040 7,170 1,300 7,460 2,960 9,190 6,510 12,700
APR 1,400 6,650 1,740 6,950 4,030 9,160 8,990 14,100
MAY 11,300 6,090 13,800 8,490 33,200 27,400 66,100 60,200
JUN 21,700 5,680 26,300 10,200 63,700 47,500 120,000 104,000
JUL 20,000 6,980 24,000 10,800 60,500 47,200 122,000 108,000
AUG 17,800 11,900 21,400 15,400 54,200 48,400 109,000 103,000
SEP 11,300 10,100 13,700 12,700 34,900 34,100 72,800 72,000
OCT 5,100 7,020 6,320 8,240 15,900 18,000 36,000 38,100
NOV 2,150 7,520 2,670 7,990 6,490 11,900 14,400 19,800
DEC 1,520 8,540 1,890 8,750 4,490 11,300 9,510 16,300
Annual 8,010 7,990 9,720 9,660 24,100 24,000 48,600 48,500
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Monthly Average Flow Comparison (cfs)
JAN 1%
FEB 1%
MAR 1%
APR 1%
MAY 12%
JUN 23%
JUL 21%
AUG 19%
SEP 12%
OCT 5%
NOV 2%
DEC 2%
Watana Dam (Pre-Project)
JAN 9%
FEB 10%
MAR 8%
APR 7%
MAY 6%
JUN 6% JUL
7%
AUG 12%
SEP 11%
OCT 7%
NOV 8%
DEC 9%
Watana Dam (Max LF OS-1)
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Monthly Average Flow Comparison (cfs)
JAN 8%
FEB 8%
MAR 7%
APR 6%
MAY 7%
JUN 9%
JUL 9%
AUG 13%
SEP 11%
OCT 7%
NOV 7%
DEC 8%
Gold Creek (Max LF OS-1)
JAN 1%
FEB 1%
MAR 1%
APR 2%
MAY 12%
JUN 23%
JUL 21%
AUG 18%
SEP 12%
OCT 5%
NOV 2%
DEC 2%
Gold Creek (Pre-Project)
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Monthly Average Flow Comparison (cfs)
JAN 4% FEB
4%
MAR 3%
APR 3%
MAY 10%
JUN 17%
JUL 16%
AUG 17%
SEP 12%
OCT 6%
NOV 4%
DEC 4%
Sunshine (Max LF OS-1)
JAN 1%
FEB 1%
MAR 1%
APR 1%
MAY 12%
JUN 22%
JUL 21%
AUG 19%
SEP 12%
OCT 6%
NOV 2%
DEC 2%
Sunshine (Pre-Project)
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Monthly Average Flow Comparison (cfs)
JAN 3%
FEB 3%
MAR 2% APR
2%
MAY 10%
JUN 18%
JUL 19%
AUG 18%
SEP 12%
OCT 7%
NOV 3%
DEC 3%
Susitna Station (Max LF OS-1)
JAN 1%
FEB 1%
MAR 1%
APR 2%
MAY 11%
JUN 21%
JUL 21%
AUG 19%
SEP 13%
OCT 6%
NOV 2%
DEC 2%
Susitna Station (Pre-Project)
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Annual Flow Duration
Watana Dam (PRM187) Gold Creek (PRM 140)
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Annual Flow Duration
Sunshine (PRM 87.9) Susitna Station (PRM 29.9)
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Flood Frequency Pre-Project and Max LF OS-1
Watana Dam (PRM 187) Gold Creek (PRM 140)
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Flood Frequency Pre- Project and Max LF OS-1
Sunshine (PRM 87.9) Susitna Station (PRM 29.9)
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Annual Peak Flow Comparison: Watana Dam Site (PRM 187)
Return Period (Years)
Watana Dam Site
Pre-Project Flow (cfs)
Max LF OS-1 Flow (cfs)
Difference (cfs)
Difference (%)
1.01 21,100 12,800 -8,300 -39%
1.25 27,800 14,100 -13,700 -49%
1.5 30,700 15,800 -14,900 -49%
2 34,200 20,700 -13,500 -39%
5 43,700 28,700 -15,000 -34%
20 57,600 40,200 -17,400 -30%
50 67,300 48,200 -19,100 -28%
100 75,100 54,600 -20,500 -27%
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Annual Peak Flow Comparison: Gold Creek (PRM 140)
Return Period (Years)
Gold Creek
Pre-Project Flow (cfs)
Max LF OS-1 Flow (cfs)
Difference (cfs)
Difference (%)
1.01 25,400 12,900 -12,500 -49%
1.25 35,100 14,400 -20,700 -59%
1.5 39,000 19,100 -19,900 -51%
2 43,700 23,900 -19,800 -45%
5 55,800 34,300 -21,500 -39%
20 72,300 48,800 -23,500 -33%
50 83,400 58,600 -24,800 -30%
100 92,100 66,400 -25,700 -28%
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Annual Peak Flow Comparison: Sunshine Station (PRM 87.9)
Return Period (Years)
Sunshine
Pre-Project Flow (cfs)
Max LF OS-1 Flow (cfs)
Difference (cfs)
Difference (%)
1.01 64,000 47,600 -16,400 -26%
1.25 80,200 60,500 -19,700 -25%
1.5 87,000 65,800 -21,200 -24%
2 94,700 72,000 -22,700 -24%
5 115,400 88,200 -27,200 -24%
20 143,600 110,400 -33,200 -23%
50 162,500 125,100 -37,400 -23%
100 177,300 136,700 -40,600 -23%
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Annual Peak Flow Comparison: Susitna Station (PRM 29.9)
Return Period
(Years)
Susitna Station
Pre-Project Flow (cfs)
Max LF OS-1 Flow (cfs)
Difference (cfs)
Difference (%)
1.01 131,700 109,500 -22,200 -17%
1.25 151,600 124,900 -26,700 -18%
1.5 160,400 132,900 -27,500 -17%
2 170,300 141,900 -28,400 -17%
5 197,000 168,900 -28,100 -14%
20 233,500 209,400 -24,100 -10%
50 257,600 238,200 -19,400 -8%
100 276,300 261,400 -14,900 -5%
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Shift in Return Period of Peak Flows Pre-Project vs. Max LF OS-1
Watana Dam Site (187) Gold Creek (PRM 140)
Discharge
(cfs)
Pre-Project Return Period (years)
Max LF OS-1 Return Period (years)
Discharge
(cfs)
Pre-Project Return Period (years)
Max LF OS-1 Return Period (years)
21,100 1.01 2 25,400 1.01 2
27,800 1.25 4 35,100 1.25 5
30,700 1.5 6 39,000 1.5 8
34,200 2 10 43,700 2 12
43,700 5 30 55,800 5 39
57,600 20 136 72,300 20 166
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Shift in Return Period of Peak Flows Pre-Project vs. Max LF OS-1
Sunshine (PRM 87.9) Susitna Station (PRM 29.9)
Discharge
(cfs)
Pre-Project Return Period (years)
Max LF OS-1 Return Period (years)
Discharge
(cfs)
Pre-Project Return Period (years)
Max LF OS-1 Return Period (years)
64,000 1.01 1.4 131,700 1.01 1.5
80,200 1.25 3 151,600 1.25 3
87,000 1.5 5 160,426 1.5 4
94,700 2 7 170,300 2 5
115,400 5 27 197,000 5 13
143,600 20 149 233,500 20 43
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Ratio 100-year to 2-year Peak Flows
Location Pre-Project Ratio
Max LF OS-1 Ratio
Watana Dam (PRM 187 2.2 2.6
Gold Creek (PRM 140) 2.1 2.8
Sunshine (PRM 87.9) 1.9 1.9
Susitna Station (PRM 29.9) 1.6 1.8
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The Analysis is an Initial Assessment
• Performed to assist in study planning
• Watana load is very conservative for any period of time & not realistic for an entire year
• Models will be upgraded in 2013 – Replace HEC-ResSim Muskingum-Cunge routing
– 2012 X-sections, additional 2013 X-sections
– Refine tributary inflows and accretion flows
– Additional calibration
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